JP6474262B2 - Trunnion type ball valve - Google Patents

Description

  The present invention relates to a trunnion-type ball valve, and more particularly to a trunnion-type ball valve that can maintain high sealing performance even when high pressure is applied with a large diameter.

A trunnion type ball valve is known as a valve particularly suitable for a high-pressure fluid, and is usually mounted on a body with a ball seat as a valve seat held by a seat retainer, and the ball seat is valved by the elasticity of a coil spring. It is provided in a structure in which fluid is sealed with a primary (upstream) ball sheet by being ejected in the body direction and pressed against the ball.
As this type of trunnion type valve, for example, a ball valve disclosed in Patent Document 1 is disclosed. This ball valve has a structure in which the ball seat is fixed to the seat retainer to prevent the ball seat from falling off.
The ball valve 1 shown in FIG. 5 has a structure in which the ball seat 3 is mounted on the seat retainer 2 in a state in which the ball seat 3 is prevented from falling off from the seat retainer 2. .

In the case of any of the above-described ball valves, it is required that the ball seat is in contact with the valve body that can be closed while maintaining high sealing performance.
In the ball valve of Patent Document 1, the sealing surface of the ball seat is provided with the same curvature as the sealing surface of the valve body, and the sealing surfaces of the ball seat and the valve body having the same curvature adhere to each other over the entire circumference. Trying to secure. Also in the ball valve of FIG. 5, as in Patent Document 1, the seal surface 6 in the range from the primary side seal portion 4 to the secondary side seal portion 5 formed on the ball seat 3 has a valve on the outer periphery of the ball valve body 7. It is provided with the same curvature as the body seal surface 8.
That is, in these ball valves, in FIG. 5, the spherical shape of the ball valve body 7 and the seal surface 6 of the ball seat 3 are provided with the same dimensions, and the valve body seal surface 8 is formed from low pressure to high pressure. The fluid pressure is sealed in a state where the seal surface 6 is always in surface contact in the range from the primary side seal portion 4 to the secondary side seal portion 5.

On the other hand, in Patent Document 2, the ball sheet is held in a circumferentially rotatable state by the sheet holding unit, and the ball sheet is rotated in the circumferential direction along with the rotation of the ball, thereby preventing uneven wear of the ball sheet and sealing performance. A ball valve is disclosed which attempts to prevent the deterioration of the ball.
In the ball valve of Patent Document 3, the space between the bottom surface of the seat ring and the bottom surface of the seat ring holding groove of the seat holding means is provided so as to be inclined while being inclined toward the ball side as the outer diameter is increased. The pressure deformation when the pressure is applied is absorbed into the space, thereby preventing the position of the seal portion from changing and maintaining the sealing performance.
In the above-described trunnion type ball valve, a resin material is generally used as a ball sheet at a fluid temperature ranging from room temperature to about 250 ° C. In this case, when the fluid pressure becomes high, the ball seat seals the fluid while elastically deforming according to the pressure.

JP-A-9-133225 Japanese Patent No. 3815669 Japanese Patent No. 4812091

  In the ball valve having the structure of Patent Document 1 and FIG. 5 described above, when a high pressure is applied from the flow path side after assembly and at a low pressure, the resin ball seat 3 is a seat retainer 2 as shown by the arrow in FIG. It is elastically deformed in the direction of opening outward with the contact part 9 as the center. When the ball seat 3 is elastically deformed in this way, the contact portion 9 is located on the outer diameter side in FIG. 5 with respect to the primary side seal portion 4, so the primary side seal portion 4 is centered on the contact portion 9. It moves in the direction approaching the ball valve body 7 by the rotating action that opens to the outside of the ball seat 3. As a result, as shown in FIG. 6, the seal between the ball valve body 7 and the ball seat 3 changes from the surface contact from the primary side seal portion 4 to the secondary side seal portion 5 to the line contact on the primary side seal portion 4 side. However, there is a possibility that the seal surface pressure of the primary side seal portion 4 is locally increased by this line contact seal, and the ball seat 3 is partially deformed. If the valve is rotated in this state, the primary side seal portion 4 cannot withstand the surface pressure, causing uneven wear, which easily leads to fluid leakage.

  Further, in FIG. 6, the ball seat 3 is rotated with the contact portion 9 as a base point, and the primary side seal portion 4 serving as a sealing portion is closer to the ball valve body 7 than the secondary side seal portion 5. Thus, it becomes difficult to seal the ball valve body 7 by the secondary side seal portion 5, and it is difficult to avoid an increase in local surface pressure by the primary side seal portion 4. This phenomenon becomes more noticeable as the valve becomes larger in diameter, and the sealing performance at a high pressure is remarkably deteriorated, so that it is difficult to ensure the sealing performance from a low pressure to a high pressure.

  On the other hand, in the ball valve of Patent Document 2, an attempt is made to prevent uneven wear by rotating the ball seat in the circumferential direction, and in Patent Document 3, an attempt is made to prevent a change in the position of the seal portion by absorbing the pressure deformation of the seat ring. However, in any case, when the fluid is at a high pressure, the ball seat is elastically deformed in the opening direction as in the case of the ball valve in FIG. 5, and the contact with the ball valve body approaches the line contact from the surface contact. Thus, there is a possibility that uneven wear occurs on the seal surface and the seal performance deteriorates.

  The present invention has been developed in order to solve the conventional problems. The object of the present invention is to improve the sealing performance between the ball seat and the valve body even at high pressure to prevent leakage. An object of the present invention is to provide a trunnion type ball valve that can prevent wear and improve durability.

  In order to achieve the above object, the invention according to claim 1 provides a seat retainer having a ball seat mounted on at least the upstream side of a ball having a through-hole provided in the body so that the ball can be rotated via a stem. In the provided ball valve, the ball seat is mounted in a free state in the mounting groove formed in the seat retainer, and the inner diameter dimension of the portion A, which is the fulcrum position of the back seal of the ball seat, is closer to the inner diameter than the seal portion of the ball seat. The trunnion-type ball valve is provided so that the ball seat at high pressure is elastically deformed so as to open with the A portion as a fulcrum, and the sealing portion is sealed at least in a surface contact state from the outer diameter side toward the inner diameter side.

  The invention according to claim 2 is a trunnion-type ball valve in which the positional relationship between the A portion which is a fulcrum position and the sealing portion B and the sealing portion C which are seal portions is A <C <B with respect to the inner diameter dimension. is there.

  The invention according to claim 3 is a trunnion-type ball valve in which the sealing part B maintains a line contact state and the sealing part C is in a non-contact state with the ball surface when the assembly is initial and the fluid pressure is low. .

  In the invention according to claim 4, the sealing portion of the ball seat is formed in a spherical surface, and the spherical surface is arranged on the flow axis in the body in the same manner as the center of the ball, and the inner diameter thereof is set. It is a trunnion type butterfly valve formed with a diameter smaller than the spherical shape of the ball.

  In the invention according to claim 5, a predetermined clearance is provided between the inner peripheral surface of the mounting groove and the outer peripheral surface on the seal surface side of the ball seat so that the ball seat is opened at a high pressure and excessive opening is suppressed. This is a trunnion type ball valve.

  The invention according to claim 6 is a trunnion type ball valve in which a clearance is provided between the inner peripheral surface of the locking portion formed in the mounting groove and the outer peripheral surface side of the ball seat.

  According to the first aspect of the present invention, when the ball seat mounted in a free state in the mounting groove has a fluid pressure of low pressure, the outer diameter side of the seal portion is in line contact with the ball, and in the case of high pressure, A Even if high-pressure fluid flows through a large-diameter valve, the seal performance between the ball seat and the valve element is improved by elastically deforming so that the part opens as a fulcrum and sealing the seal part in a surface contact state. Can be surely prevented. By being able to seal while minimizing the contact of the seal part to the ball, it is possible to prevent the occurrence of local surface pressure of the sealed part while preventing the inner diameter side of the seal part from being scraped off by the rotation of the ball at low pressure. Durability can be improved by preventing wear of the ball seat.

  According to the second aspect of the present invention, when the fluid pressure is low, the sealing portion B contacts the ball while preventing the sealing portion C from contacting the ball while the A portion which is the fulcrum position is sealed on the back surface. The line contact seal by the sealing portion B can prevent leakage while preventing wear of the ball sheet. When the fluid pressure is high, the ball seat is elastically deformed in the direction to open with respect to the ball around the A portion at the fulcrum position, so that the sealing portion C side contacts the ball and the outer diameter side sealing portion Surface contact from B to the inside of the sealing part C on the inner diameter side is a seal part, so that local surface pressure is prevented and uneven wear of the seal part is prevented, and the sealing property is improved and leakage is ensured. Can be prevented.

  According to the invention of claim 3, when the fluid pressure is low, the sealing portion B is prevented from coming into contact with the ball to prevent wasteful wear and to secure a sealing property capable of preventing fluid leakage. Can do.

  According to the invention of claim 4, when the fluid pressure is high, the ball seat is elastically deformed so as to open with respect to the ball, and the spherical surface of the seal portion is brought into surface contact with the outer periphery of the ball. The sealability can be improved while preventing uneven wear of the part.

  According to the fifth aspect of the present invention, it is possible to elastically deform toward the clearance side without restraining the deformation of the ball sheet at a high pressure to maintain high sealing performance, and to transmit extra stress due to contact of the mounting groove with the ball sheet. By avoiding it, the flexibility can be maintained. On the other hand, by preventing the ball seat from opening too much through the clearance, it is possible to maintain the surface contact seal state at high pressure and prevent leakage.

  According to the sixth aspect of the present invention, the ball seat can be mounted in a free state in a state in which the protrusion from the seat retainer is prevented by the locking portion, and the ball can be elastically deformed so as to be able to seal the ball from low pressure to high pressure. .

It is a longitudinal section showing an embodiment of a trunnion type ball valve of the present invention. It is an important section expanded sectional view at the time of valve closing of a trunnion type ball valve. It is an expanded sectional view which shows the state which the ball seat of FIG. 2 sealed. It is a partially omitted enlarged cross-sectional view showing the relationship between the ball and the ball seat. It is principal part sectional drawing which shows the primary side part vicinity of the conventional trunnion type | mold ball valve. It is principal part sectional drawing which shows the state which the ball seat of FIG. 5 sealed.

  Hereinafter, embodiments and operations of a trunnion type ball valve according to the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the trunnion type ball valve of the present invention, and FIG. 2 shows an enlarged cross-sectional view of the main part (upstream side) of the primary side (upstream side) when the trunnion type ball valve of FIG. 1 is closed. Yes.

  1 has a body 11, a ball 12, a stem 13, a seat retainer 14, and a ball seat 15, and particularly has a large diameter and a class (nominal pressure). It is suitable for use as a high pressure fluid of about 150 to 2500.

The body 11 has an annular body 20 and annular caps 21, 21 on both sides, which are made of carbon steel, stainless steel, etc., and are integrated by bolts and nuts 22.
In the body 11, a ball 12 is rotatably provided via a stem 13 including an upper stem 12 a and a lower stem 13 b, and a seat retainer 14 is disposed on both the balls 12, that is, on the upstream and downstream sides. A ball seat 15 is attached to the seat retainer 14. The ball 12 is made of stainless steel, and is provided with a through hole 12 a that can communicate with the flow path 23 in the valve body 10. In the present embodiment, the ball sheet 15 and the seat retainer 14 are attached to the upstream and downstream sides of the ball 12, but these may be provided at least on the upstream side. In the case of the ball valve body 10 in which the ball seat 15 and the seat retainer 14 are mounted on the upstream and downstream sides as shown in FIG. 1, either the right side or the left side in the drawing may be the primary side.

In FIG. 2, a ball sheet 15 is formed in an annular shape that can be elastically deformed by a resin material such as PTFE (polytetrafluoroethylene), nylon, and PEEK (polyether ether ketone). A seal site 25 is provided.
The ball seat 15 is mounted in a free state in a mounting groove 26 formed in a seat retainer 14 to be described later, and the ball seat 15 is provided on the mounting groove 26 side of the ball seat 15 so as to be in contact with the mounting groove 26 and to be sealed on the back surface. A portion serving as a fulcrum position is formed to project annularly.

  In the present invention, “the ball seat 15 is mounted in a free state in the mounting groove 26 formed in the seat retainer 14” means that the ball seat 15 is prevented from jumping out of the mounting groove 26 and is a fulcrum. A state in which the ball 12 side is mounted in a state in which the ball 12 can be elastically deformed in the direction of opening and movable in the direction of the flow path axis P of the valve body 10.

  The inner diameter dimension L1 of the A portion is provided closer to the inner diameter than the seal portion 25 of the ball seat 15, and the bottom of the ball seat 15 and the mounting groove 26 is formed by the A portion protruding in a ring shape in this way. A gap H is formed between the holes 34. The ball seat 15 is elastically deformed so as to open at a portion A as a fulcrum at high pressure, and is provided so as to seal the seal portion 25 at least in a surface contact state from the outer diameter toward the inner diameter side. At this time, by providing the gap H, the gap H also contributes to the rotating action when the ball seat 15 is elastically deformed so as to open.

  The seal portion 25 is formed by a spherical portion that is a spherical surface that can come into surface contact with the outer periphery of the ball 12, and a sealing portion C is formed on the primary side of the seal portion 25 in the flow path 23 direction, and a sealing portion B is formed on the secondary side. In addition, the sealing portion B is provided so as to be in line contact with the ball 12 at the time of low pressure.

  The positional relationship between the A portion that is the fulcrum position and the sealing portion B and the sealing portion C that are the seal portions 25 is when the inner diameter dimension of the sealing portion B is L2 and the inner diameter dimension of the sealing portion C is L3. The inner diameter dimension L1 <the inner diameter dimension L3 <the inner diameter dimension L2 so that A <C <B with respect to the inner diameter dimensions of the A portion, the sealing portion B, and the sealing portion C.

  Furthermore, as shown in FIG. 2, when the ball seat 15 is mounted in the mounting groove 26 and when the fluid pressure is low, the inner diameter φDS from the sealing portion C to the sealing portion B of the seal portion 25 is Unlike the ball diameter φDB of the ball 12, these are formed to have different diameter dimensions. In the present embodiment, the inner diameter φDS is smaller than the ball sphere diameter φDB, that is, the seal portion inner diameter φDS <the ball sphere diameter φDB. The center P1 of the inner diameter φDS and the center P2 of the ball sphere diameter φDB are both disposed on the flow path axis P of the valve body 10, as shown in FIG.

  As a result, in the initial stage of assembly and when the fluid pressure is low, the contact of the sealing portion B with the ball 12 is maintained in a line contact state, and the sealing portion C is not in contact with the ball surface 16.

  A predetermined clearance G is provided between the inner peripheral surface 26a of the mounting groove 26 and the outer peripheral surface 15a on the seal surface side of the ball seat 15, and the ball seat 15 is opened to the clearance G side at high pressure. , Too much opening is suppressed.

  On the outer peripheral surface 15 a of the ball seat, a projecting engagement portion 32 is formed on the back side of the mounting groove 26 so as to be approximately half the length in the mounting direction of the ball sheet 15. On the other hand, in the mounting groove 26 of the seat retainer 14, a projecting locking portion 33 is formed from the opening side to approximately half the length of the mounting groove 26. The clearance G is provided at least between the inner peripheral surface 26 a of the locking portion 33 and the outer peripheral surface 15 a side closer to the ball 12 than the engaging portion 32 of the ball seat 15.

As shown in FIG. 1, the seat retainer 14 is provided in a substantially cylindrical shape by a metal material such as carbon steel or stainless steel, and is formed so that the mounting side of the ball seat 15 described above has a slightly larger diameter. Is provided with an annular mounting groove 26 into which the ball seat 15 can be inserted.
A bottomed hole 34 having a diameter larger than the outer diameter of the engaging portion 32 is provided on the back side of the locking portion 33, and the depth of the bottomed hole 34 is formed larger than the length of the engaging portion 32. The inner diameter of the bottomed hole 34 is slightly larger than the outer diameter of the engaging portion 32.

  In the seat retainer 14, the ball seat 15 is mounted in the mounting groove 26 in a state where the engaging portion 32 is accommodated in the bottomed hole 34. After the mounting of the ball seat 15, the rear end side of the engaging portion 32 and the rear end side of the locking portion 33 are opposed to each other so as to be locked in the loading direction of the engaging portion 32. The ball seat 15 is in a free state while being prevented from jumping out of the groove 26. A coil spring 40 is mounted between the seat retainer 14 and the cap 21 in a resilient state on the side opposite to the ball seat 15 mounting side. Thereby, the ball sheet 15 is pressed against the ball 12 by the coil spring 40 via the seat retainer 14. The seat retainer 14 and the cap 21 are sealed with an O-ring 41 and a packing 42.

  After the ball seat 15 is mounted on the seat retainer 14, the communication portion that communicates the cavity 35 and the upstream side of the ball 12 between the inner peripheral surface 15 b side and the outer peripheral side (engagement portion 32 side) of the ball seat 15. 36 is provided. As a result, excessive pressure due to abnormal pressure increase in the cavity 35 of the valve main body 10 when fully closed or fully opened is moved in the opposite direction to the ball 12 by the self-tensioning force of the seat retainer 14 and is within the mounting groove 26. The ball sheet 15 is pushed out to the ball 12 side by the fluid pressure flowing into the back surface side of the ball sheet 15, and at this time, the abnormal pressure increase in the cavity 35 is relieved in the flow path 23 through the communication portion 36. Here, the abnormal pressure increase in the cavity 35 means that the temperature of the fluid rises or the environment in which the valve main body 10 is installed becomes high, so that the body 11 and the ball 12 in the valve main body 10 in the valve closed state. , A phenomenon in which the pressure in a closed space (cavity 35) surrounded by the ball seat 15, the seat retainer 14 and the like increases.

  The trunnion type ball valve of the present invention is suitable for a large diameter of 8 inches or more. In this embodiment, for example, in the case of a valve body 1 of class 600 size 12B, ball seat material: PTFE, ball ball Diameter: φ460 mm, the inner diameter φDS of the seal part is reduced by about 3% to 5% with respect to the ball ball diameter φDB, and the inner diameter (inner diameter dimension L3) of the sealing part C and the inner diameter of the A part (inner diameter dimension). Dimensional difference from L1): 2 mm or less (1 mm or less in the radial direction), Dimensional difference between the inner diameter (inner diameter dimension L2) of the sealing part B and the inner diameter (inner diameter dimension L3) of the sealing part C: 2 mm or more (radial direction) 1 mm or more). In this case, it is assumed that the elastic deformation that opens to the ball 12 side of the ball sheet 15 at the time of high-pressure load is expanded by about 1 °.

  The sealing portion 25 of the ball seat 15 is provided in the vicinity of the seal to the ball 12 and has a shape other than the spherical portion as long as the ball 12 can be sealed by line contact or surface contact according to the height of the fluid pressure. For example, it may be formed in a taper shape or a circular arc shape.

Although not shown in the drawings, the engaging portion 32 of the ball seat 15 and the engaging portion 33 of the seat retainer 14 are respectively formed with a male screw and a female screw that can be screwed to each other, and the ball is passed through the male screw and the female screw. The sheet 15 may be mounted in the mounting groove 26.
When an internal thread is provided in the locking portion 33, the inner peripheral surface 26a becomes a thread. The ball seat 15 that is elastically deformed at high pressure has the outer peripheral surface 15a that is not easily threaded, so that the ball seat 15 jumps out of the mounting groove 26 or floats up when the valve body 1 is opened or closed under high pressure. And the durability of the ball sheet 15 can be further improved.

  Although not shown, for a large-diameter valve of size 10B or more, a groove or hole that can be tightened or removed by a tightening jig may be provided on the outer periphery of the ball seat 15, and in this case, the ball seat 15 can be easily assembled.

  When the ball seat 15 is mounted on the seat retainer 14, the ball sheet 15 is inserted from the opening side toward the mounting groove 26 so as to push the engaging portion 32 into the locking portion 33. When the engaging portion 32 reaches the bottomed hole 34, the mounting of the ball seat 15 is completed, and the ball seat 15 is prevented from being detached from the seat retainer 14 and mounted in a free state. At this time, as described above, since the depth of the bottomed hole 34 is larger than the length of the engaging portion 32, the engaging portion 32 surely exceeds the region of the locking portion 33, and the engaging portion 32 is It is accommodated in the bottomed hole 34.

After the ball seat 15 is inserted, a clearance G is formed between the ball seat 15 and the mounting groove 26, and this clearance G enables elastic deformation in the direction in which the ball 12 side of the ball seat 15 opens around the A portion serving as a fulcrum position. Become.
As shown in FIG. 2 between the engaging portion 32 and the locking portion 33, a space S is provided in the loading direction (the direction of the flow path axis P of the flow path in FIG. 1). Since the inner diameter of the bottomed hole 34 is slightly larger than the outer diameter of the engaging portion 32, a radial gap L is also provided between them. Due to this gap L, the ball seat 15 can advance and retreat in the space S of the seat retainer 14 with a low sliding resistance.

  The dimensions such as the size of the clearance G, the space S, and the gap L are set in consideration of the environmental temperature at the time of assembly and the temperature difference due to the difference in the assembly location. In the case of this embodiment, it is provided so as to be able to cope with an assembly temperature of a maximum of 40 ° C. in the summer and a minimum of 10 ° C. in the winter.

Next, the operation of the above-described embodiment of the trunnion type ball valve of the present invention will be described.
In the valve body 10 of FIG. 1, when the fluid pressure upstream of the flow path 23 is low, the A portion of the ball seat 15 is in contact with the bottom surface side of the mounting groove 26 as shown in FIG. Thus, the sealed portion B is kept in line contact with the ball 12 and sealed. This line contact seal has a lower sealing force than a surface contact seal, but since the fluid is at a low pressure, it does not reach the yield point of the ball seat material, so wear that impairs the seal performance does not occur. The leakage at the low pressure is surely prevented.

  When a high fluid pressure is applied, the ball retainer 14 is pushed further toward the ball 12 because the seat retainer 14 is applied with a self-tightening force utilizing a high fluid pressure in addition to the elastic force of the coil spring 40. As shown in FIG. 4, the ball seat 15 is elastically deformed in the direction in which the ball 12 is opened around the A portion according to the height of the fluid pressure, and the ball 12 is directed from the outer diameter side toward the inner diameter side. By sealing at least in a surface contact state, a high-pressure fluid can be reliably sealed.

  In this case, in FIG. 2, the positional relationship between the A portion that is the fulcrum position and the sealing portion B and the sealing portion C that are the seal portions is A <C <B with respect to the inner diameter dimension, and is outside the A portion. Since the sealing portion B is positioned on the radial side, the sealing portion B side rotates counterclockwise so that the sealing portion B side moves in a direction away from the ball 12 in the rotational action of FIG. The side of the sealing portion C that has been separated is surely brought into surface contact with the ball 12.

  By providing a predetermined clearance G between the mounting groove 26 and the ball seat 15, it is possible to prevent the operation when the seal portion 25 side is deformed in the opening direction from being hindered, and the ball seat 15. When the outer peripheral surface 15 a comes into contact with the inner peripheral surface 26 a of the mounting groove 26, it is possible to prevent the ball seat 15 from opening too much and ensure a sealed state to the ball 12.

  Furthermore, by utilizing the structure in which the ball sheet 15 is mounted in the mounting groove 26 in a free state, the communication portion 36 is provided between the inner peripheral surface 15b of the ball sheet 15 and the mounting groove 26. The excess pressure due to abnormal pressure increase in the cavity 35 can be relieved in the flow path 23 through the communication portion 36. As a result, it is not necessary to relieve abnormal pressure increase in the cavity 35 from between the ball seat 15 and the ball 12, and the wear of the ball seat 15 and the ball 12 can be suppressed to ensure the sealing performance and the durability can be improved.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to the description of the embodiment, and the scope does not depart from the spirit of the invention described in the claims of the present invention. Thus, various changes can be made.

DESCRIPTION OF SYMBOLS 10 Valve body 11 Body 12 Ball 12a Through-hole 13 Stem 14 Seat retainer 15 Ball seat 15a Outer peripheral surface 16 Ball surface 25 Sealing part 26 Mounting groove 26a Inner peripheral surface A part Supporting point B, C Sealing part G Clearance L1, L2, L3 inner diameter

Claims (6)

  In a ball valve provided with a seat retainer mounted with a ball seat on at least the upstream side of a ball having a through-hole provided in a body, the ball seat is provided to be rotatable through a stem. It is mounted in a free state in the formed mounting groove, and the inner diameter dimension of the A portion, which is the fulcrum position of the back seal of the ball seat, is provided closer to the inner diameter than the seal portion of the ball seat. A trunnion-type ball valve characterized in that it is elastically deformed so as to open as a fulcrum and seals the seal portion from the outer diameter side to the inner diameter side at least in a surface contact state.   2. The trunnion type ball valve according to claim 1, wherein a positional relationship between the A portion that is the fulcrum position and the sealing portion B and the sealing portion C that are the sealing portions is A <C <B with respect to the inner diameter dimension.   3. The trunnion-type ball valve according to claim 2, wherein when the assembly is initial and the fluid pressure is low, the sealing portion B maintains a line contact state and the sealing portion C is not in contact with the ball surface. The ball seat seal portion is formed in a spherical surface, and the spherical surface is arranged on the flow axis in the body in the same manner as the center of the ball, and its inner diameter is smaller than the spherical shape of the ball. The trunnion-type ball valve according to any one of claims 1 to 3, wherein the trunnion-type ball valve is also formed with a reduced diameter.   2. A predetermined clearance is provided between an inner peripheral surface of the mounting groove and an outer peripheral surface on the seal surface side of the ball seat so that the ball seat is opened at a high pressure and excessive opening is suppressed. Trunnion type ball valve as described in 1.   The trunnion-type ball valve according to claim 5, wherein a clearance is provided between an inner peripheral surface of the engaging portion formed in the mounting groove and an outer peripheral surface side of the ball seat.

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